This invention pertains to the field of the absorption refrigerating machines.
According to the known basic principles of operation of the prior art absorption refrigerating machines, an absorption heat pump operates by delivering, at an average temperature level T.sub.2, a heat amount Q.sub.2 greater than a heat amount Q.sub.1 supplied thereto at an average temperature level T.sub.1 higher than T.sub.2, while receiving heat from a heat source at an average temperature level T.sub.3, lower than T.sub.2, this heat source being, for example, underground water or outside air.
A prior art type system may operate according to the basic embodiment shown in schematic form in FIG. 1. The cycle operates with a working fluid, for example, ammonia as the solute, and a solvent, for example, water.
The working fluid is vaporized by heating the solution contained in the boiler B01 and supplying of the heat amount Q.sub.1 through the exchanger E.sub.1. The resulting vapor usually contains some solvent and is rectified by contact with the reflux stream supplied at the top of the rectification zone R.sub.1. The vapor discharged from the top of the rectification zone R.sub.1 thus consists of a practically pure working fluid. This vapor condenses in the exchanger E.sub.2, while heating an external fluid supplied through duct 1 and discharged through duct 2. The resultant condensate is collected in the drum B.sub.1. A portion of this condensate is discharged through duct 3 and fed as reflux through pump P.sub.1 to the top of the rectification zone R.sub.1. The remaining portion is discharged through duct 4, expanded through the expansion valve V.sub.1 and fed through duct 5 to the exchanger E.sub.3. In the exchanger E.sub.3, it vaporized while receiving heat from an external fluid fed through duct 6 and discharged through duct 7. The vapor phase is discharged through duct 8, absorbed in a lean solution which is supplied from the boiler B01 valve V.sub.2 and duct 9 and the lean solution with absorbed vapor phase delivers heat to an external fluid fed through duct 10 and discharged through duct 11. The resultant concentrated solution is collected in the drum B.sub.2 and fed through the pump P.sub.2 and the duct 12 to the boiler B01. The concentrated solution fed to the boiler exchanges heat, in the heat exchanger E.sub.5, with the lean solution discharged from the boiler.
This arrangement is generally satisfactory when the plant operates by supplying cold and expelling heat in the exchangers E.sub.2 and E.sub.4 at a relatively low temperature of, for example, 30.degree. to 40.degree. C. When the plant is used for heating, the heating fluid is usually water whose inlet temperature in the exchangers E.sub.2 and E.sub.4 varies throughout the year. When the heat pump supplies the entire or at least a large part of the heat required for heating, the water outlet temperature may reach values of about 50.degree. C. or more. In that case, when the working fluid is ammonia or a fluid having similar boiling and critical temperatures, the pressures in the generator and in the condenser E.sub.2 increase quickly when the outlet temperature of the heated fluid itself increases. For example, in the case of ammonia, the following values of pressure are observed when the temperature increases:
______________________________________ t (.degree.C.) 30 40 50 60 70 p (atm) 11.89 15.85 20.73 26.66 33.77 ______________________________________
The relatively high pressures attained when the temperature exceeds 50.degree. C. makes the construction of the device more difficult and increases the cost.
A modification of this known process consists of vaporizing only a portion of the working fluid in the vaporizer E.sub.3 ; the entire residual liquid phase is then fed back to the desorption zone (U.S. Pat. No. 2,392,894, No. 4,003,215 and No. 4,037,649; FR Pat. No. 2 412 800; European Pat. No. 1 272). This modification does not cope with the above disadvantage.